Field of the Invention
The present invention relates to a method for automatically pursuing an object by a video camera and, particularly, to a method for automatically pursuing an object by detecting a position of the object on the basis of its specific color and rotating a video camera according to the directed position.
Description of the Related Art
In case where a moving object is pursued by a video camera, it is difficult to pursue the object by manually control the video camera when a moving range of the object is extensive or its moving speed is high. In view of this fact, an automatic pursuing device capable of controlling a rotation (panning horizontally or vertically or both) of a video camera is highly desired.
For example, in a case where an object to be pursued is an animal, a player of a ball game or a ball itself, a movement thereof is usually unpredictable. Therefore, in order to pursue such unpredictable movement, a camera-man who operates a video camera is required to be highly skilled, otherwise, there causes a missing object out of a camera image (a video image produced by a video camera, which corresponds to a full field of vision viewed and taken by the video camera) or such object not located at a center portion of the camera image as desired, if not missed from the camera image.
Further, when the operator himself is the object or desired to be shot together with an other object, such automatic pursuit device is highly desired.
To this end, various automatic pursuing methods have been proposed, such as a method in which a video camera is directed to an object generating sound as a guidance marker which is louder than the environment or a method in which a video camera pursues infrared ray emitted from an infrared emitter carried by the object as a guidance marker.
In these methods, an audio signal or an optical signal obtained from a microphone or an infrared light receiving section which is equipped on a video camera is analyzed to obtain a position of the sound source or the light source and the video camera is automatically rotated according to the detected position as such that its line of sight is directed to the source. Such methods have been used to date.
Such conventional methods have drawbacks or demerits such as follows:
The method utilizing sound is completely ineffective to any object which does not produce sound or when such object stops sounding. The sound pursuing method is also ineffective if there is another sound source or sources which may sound louder than or interfere with the sound of the intended object so that the direction of the video camera is confused.
On the other hand, in the infrared pursuing method, it is necessary to provide an infrared light source on the object. This may be achieved by preparing a portable light source separately from the video camera and providing a light receiving device on the video camera. However, this causes the construction of the system to be complicated and expensive.
As mentioned in the foregoing, these method have limitations, as it can not be applied practically to an object such as animal or ball in a ball game.